The present invention relates to improvements in flexible containers, and in particular, to guide strips for an easy-open container.
Reclosable flexible containers are well-known in the art. Such containers typically comprise a bag-like structure made from a folded web or tube of thermoplastic film material. Thermoplastic sheet or tube having male and female interlocking zipper elements, as is known in the art, is typically folded, severed and sealed along two side edges, and closed with the zipper elements across the bag mouth, as for example in U.S. Pat. Nos. 3,371,696 to Ausnit, and U.S. Pat. No. 3,198,228 to Naito.
Because accessible by their very nature, reclosable flexible containers have further been developed which remain completely sealed across the lips of the bag until used. Tear strips are known, such as shown by Staller et al, U.S. Pat. No. 3,543,343, for tearing across the bag lips. Thus, the container remains completely sealed until the user employs the tear strip to gain access to the mouth of the flexible container.
Of further relevance is Ausnit et al, U.S. Pat. No. 4,812,074, wherein a film containing interlocking zipper elements is sealed to a web of thermoplastic material forming a two-layered area of film and web. Folding the web brings the zipper elements into opposing relationship with the film layer inside and the web layer outside the top edge of the container which results. The film, thus, does not serve alone to seal the edge of the container. The '074 patent further discloses a tear strip located in the film by which both the film and web may be torn to gain access to the bag contents.
While such tear strips allow the container to remain air-tight and tamper-proof until initial use, problems have arisen in their use. Such problems include consumers' inability to tear the thermoplastic film material; the need to use scissors to open the container, obviating the value of the tear strip; and irregular tearing, which compromises zippered portions of the containers. Modifications, such as inclusion of perforations along the tear line, have enhanced the efficacy of tear strips, but eliminate the air-tight and tamper-proof features desired in completely sealing the mouth of such containers.
Another approach to hermetically sealing the mouth opening of flexible containers has been the attachment of separate films or membranes over the mouth of a bag-like structure so that the membrane serves as the top edge of the container. See, for example U.S. Pat. No. 4,874,257 to Inagaki, and U.S. Pat. No. 4,927,271 to Branson. Thereafter, the membrane which forms the seal may be ruptured to gain entry to the bag contents. Access to the container of Inagaki is evidently by cutting since no means for opening the hermetic seal are disclosed. Branson, U.S. Pat. No. 4,971,271, discloses a tamper-evident hood closure which is opened by separating the hood closure from the bag along perforated lines of tearing disposed on both side walls of the hood closure. By virtue of its perforations, however, the tamper-evident hood closure of Branson does not hermetically seal the container.
Accordingly, the need remains for further improvement in the design of tear strips for easy-opening of sealed flexible containers of thermoplastic material.